The subject matter of this invention relates to sonic well tools, and, more particularly, to a transmitter and receiver array for a sonic well tool.
Some well tools are used in boreholes of oil wells for the purpose of determining if oil exists in a formation surrounding the borehole. Some well tools are sonic in nature, in that they transmit a sonic compressions or shear wave into the formation and receive the sonic compressional or shear waves from the formation. One such prior art sonic well tool is known as the "Array Sonic Service" tool, or a "Sonic Digitizing Tool (SDT)". A partial view of the SDT tool, illustrating only the receiver section of the tool, is shown in FIG. 3A of the drawings. The SDT tool included a transmitter section, but each of the transmitters of the SDT tool were monopole transmitters. There were no dipole transmitters in the SDT array sonic service tool. Consequently, the data received by the SDT tool receivers comprised solely of monopole wave data. Furthermore, the SDT tool was not designed to attenuate or delay, to any substantial degree, flexural and compressional waves propagating along the body of the tool to the receivers. Consequently, the SDT tool body of the tool to the receivers. Consequently, the SDT tool receivers would sense monopole related waves, propagating along the borehole formation, but would also sense undesirable disturbances in the tool created by flexural and compressional waves propagating along the body of the tool. The SDT tool did delay, to some extent, compressional waves propagating along the body of the tool, but did not appear to delay flexural waves propagating along such tool. Therefore, a new sonic tool is needed to transmit sonic dipole as well as monopole related waves into a surrounding borehole formation, to be capable, at a receiver end of such tool, of receiving sonic monopole waves when the sonic tool transmits sonic monopole related waves into the borehole formation and of receiving sonic dipole waves when the sonic tool transmits sonic dipole related waves into the borehole formation, and to attenuate and delay, to a maximum extent possible, all compressional and flexural waves propagating along the inner and outer bodies of the sonic tool.